Acid test kit

ABSTRACT

An acid test kit uses an indicator paper in a transparent tube which is easily and temporarily inserted in a Schrader-valve at a compressor suction inlet of a refrigeration system. The simplicity, yet sufficient accuracy, of the kit permits several different ways of holding the paper in the tube through a friction fit. One way is to sandwich the paper between a tapered holder which is folded to provide a nose for actuating the Schrader valve. Another way is to provide the paper on or over a cylindrical member. A method for using the test kit including allowing vapor refrigerant from the system to pass through the tube to the atmosphere.

BACKGROUND AND SUMMARY OF THE INVENTION

[0001] The present invention relates to an acid test kit and, moreparticularly, to an acid test kit used in vapor compressionrefrigerators and the like in which an indicator paper is held in atransparent tube-like fixture to monitor the acid level in the systemsimply, quickly and inexpensively.

[0002] Vapor compression refrigerators, heat pumps, and air conditionersmust always be concerned with the presence of acids in the refrigerantwhich can severely shorten the life of both the compressor and therefrigerant. These acids can be formed by chemical reactions withcomponents and/or materials of construction, lubricating oils, and/orimpurities. The instability of the refrigeration, and thus the formationof acids, is accelerated by elevated temperatures which result fromimproper operation, such as a failed condenser fan, or clogged air flowpath.

[0003] Checking the refrigerant and/or oil acid is a common maintenanceprocedure because acidic refrigerant can be cleaned up before permanentdamage to the hardware and refrigerant occur. Acidic refrigerant willalso result in hermetic compressor motor burn-out because the acid willdegrade the motor winding's electrical insulation. Moreover, thepresence of acid indicates the existence of other decompositionproducts, such as non-condensable gases, which result in elevatedpressures and increased compressor pressure ratios leading to reducedefficiency and overloaded compressor operation.

[0004] To avoid the above-mentioned problems, refrigeration systems aretested for acid content. Typically, the oil would be tested for acid,because the highest concentration of acid is found in the oil of anon-operating system (shut down). It is, however, much easier to testthe refrigerant for acid instead of testing the oil for acid, since therefrigerant is pressurized and existing service valves provide an easyway of sampling the refrigerant. Testing of the refrigerant vapor,rather than the refrigerant liquid, of the system is much moreconvenient because testing the liquid refrigerant results in a muchgreater refrigerant loss and the exiting liquid will cause frostbite ifnot properly handled.

[0005] Visual sensors or indicators for use in detecting the corrosivestate of a fluid in a heat exchanger system are known as seen, forexample, in U.S. Pat. No. 5,127,433. A permanently installed sensor hasa sight glass or window through which corrosiveness is determined byviewing a flap or ball displaying a color indicating either the need tochange the fluid or to add corrosion inhibitors. Alternatively,corrosiveness can be indicated by a ruptured or broken diaphragm locatedbetween the sight glass and the fluid. This form of sensor is limited toapplications such as automobile cooling systems where the sensor isprovided in the overflow conduit or in the hot fluid conduit upstream ofthe radiator.

[0006] Humidity and corrosion indicators for packaged goods in whichthin cobaltous chloride film is used as the sensing element aredescribed in U.S. Pat. No. 3,084,658. An elastomeric grommet sealed by atransparent disk is inserted into an opening in a package wall. A diskimpregnated with the cobaltous chloride is secured beneath a window andcan be replaced.

[0007] With respect to closed refrigeration systems, other types ofindicator systems are known for testing the presence and concentrationof contaminants in a refrigerant. For example, U.S. Pat. Nos. 4,923,806and 5,071,768 show apparatuses for testing liquid or vapor contaminantsin a closed system regardless of whether the apparatus is operating ornot. A disposable testing tube made of transparent material is used atthe end of a compressor discharge line or elsewhere in the system. Onesection of the tube is provided with water removal and moistureindicating chemicals, such as cobaltous chloride and another section isprovided with acid indicating chemicals such as a solution ofbromophenol blue, ethanol and glycerol. This construction is relativelycomplicated and requires a separate, specially configured flowrestrictor in addition to a tube holder, and an expensive testing tubein which the multiple contaminant testing chemicals and filter screensare permanently located.

[0008] Likewise, U.S. Pat. No. 5,377,496 shows an acid contaminationindicator for closed loop vapor compression refrigeration systems inwhich the indicator is permanently or removably installed in the bypassline around the system compressor where the refrigerant is always in thegaseous phase. A casing has a visual indicator bed of bromophenol blueas the acid indicating medium which is contacted by the refrigerantafter flowing through a filter and a flow restrictor orifice. Porousretainer disks are held against the bed by springs. Moreover, theindicator, which changes color when exposed to acids or bases, aresolid, and thus they must be exposed to the test stream in some fashion.Accordingly, this solid indicator must be mixed with an inert substanceto provide some porosity, contact surface area and increased volume andthen packaged in a clear tube. The vapor refrigerant is then passedthrough the porous mixture arranged in a bypass loop between the suctionand discharge ends of a compressor or in the main refrigerant flow pathbetween the compressor discharge and a heat exchanger to observe a colorchange. Again, we have recognized that this is an unduly complicatedconstruction which requires a substantial outlay for installation.

[0009] Another type of contaminant detector is marketed by RefrigerationTechnologies of Fullerton, Calif. under the trademark “CHECKMATE”. Aspecific volume of gas passes through a detection tube at apredetermined termination pressure. However, an expensive sealed Pyrexdetection tube containing a color-changing chemical and whose ends arepierced when fully assembled can only be used once even when the test isnegative, and thus this approach entails considerable expense regardlessof its technical merits.

[0010] In a vapor-compression system, refrigerant flows from thecondenser to the expansion valve, where it flashes into a two-phasemixture and then enters the evaporator. Superheated refrigerant vapor,with some entrained oil, leaves the evaporator and is compressed in thecompressor, before being condensed in the condenser to complete thecycle. When in chemical equilibrium, the majority of the acid in thesystem is contained in the oil, but acid is also present in the liquidand vapor refrigerant. The presence of water in the system, which is avery real possibility, causes an even greater concentration of the acidin the liquid rather than in the vapor. To further complicate theproblem, the relative liquid and vapor acid concentrations are afunction of the system's liquid and vapor volume and therefore aresystem dependent. These factors all render the measurement of acid levelin the refrigerant's equilibrium vapor phase an uncertain indication ofacid level in the compressor oil.

[0011] Although the acid content in the refrigerant vapor can not beexactly correlated to the compressor oil acid content, it is, however,accurate enough to indicate the relative status of the oil in thesystem. It is clear that when acid is detected in the vapor, the acidlevel in the oil is significantly higher. Independent of the system, itcan be generally stated that a refrigerant vapor acid level about 1-2parts per million (ppm) in the refrigerant vapor clearly means the oilacid content is high, and the system should be cleaned up to reduce theacid level. Furthermore, a refrigerant vapor acid of 10 ppm, clearlyindicates the compressor's oil acid level is well beyond safe operatinglevels and the system will fail shortly if the refrigerant and acid isnot changed or cleaned.

[0012] We have discovered that a pH paper can provide a simple fast andextremely inexpensive way to test for acidity in a refrigeration system.It allows for testing with the system on or off, and in otherapplications as well. In addition, it does not have to be installed in aline but can be temporarily connected with, for example, aSchrader-valve to permit venting of a small amount of gaseousrefrigerant to the atmosphere. This is a surprising discovery because apH paper is typically used to measure the concentration of hydroniumions in an aqueous solution. However, an aqueous solution is not presentin a refrigerant system. Table 5-30 of Lange's Handbook of Chemistry(13th Edition) lists several chemical compounds for colorimetric pHindicators as follows: Indicator Chemical Name pH Range pK_(a) λ_(max)^(nm) Color Change Cresol red (acid range) o-Cresolsulfonephthalein 0.2to 1.8 R-Y Cresol purple (acid range) m-Cresolsulfonephthalein 1.2 to2.8 1.51 533, . . . R-Y Thymol blue (acid range) Thymolsulfonephthalein1.2 to 2.8 1.85 544, 430 R-Y Tropeolin 00 Diphenylamino-p-benzene 1.3 to3.2 2.0 627, . . . R-Y sodium sulfonate 2,5-Dinitrophenal2,8-Dinitrophenol 2.4 to 4.0 3.69 C-Y 2,4-Dinitrophenol2,4-Dinitrophenol 2.5 to 4.3 3.90 C-Y Methyl yellowDimethylaminoazobenzene 2.9 to 4.0 3.3 508, . . . R-Y Methyl orangeDimethylaminoazobenzene 3.1 to 4.4 3.40 622, 464 R-O sodium sulfonateBromophenol blue Tetrabromophenolsulfone- 3.0 to 4.8 3.85 436, 592 Y-BVphthalein Bromocresol green Tetrabromo-m-cresol- 4.0 to 6.8 4.58 444,617 Y-B sulfonephthalein Methyl red o-Carboxybenzeneazo- 4.4 to 6.2 4.95530, 427 R-Y dimethylaniline Chlorophenol red Dichlorophenolsulfone- 5.4to 6.8 6.0 . . ., 573 Y-R phthalein Bromocresol purpleDibromo-o-cresolsulfone- 5.2 to 6.8 6.3 433, 591 Y-P phthaleinBromophenol red Dibromophenolsulfone- 5.2 to 6.8 . . ., 574 Y-Rphthalein p-Nitrophenol p-Nitrophenol 5.3 to 7.6 7.15 320, 405 C-YBromothymol blue Dibromothymolsulfone- 6.2 to 7.6 7.1 433, 517 Y-Bphthalein Neutral red Aminodimethylaminotolu- 6.8 to 8.0 7.4 R-Yphenazonlum chloride Phenol red phenolsulfonephthalein 6.4 to 8.0 7.9433, 558 Y-R m-Nitrophenol m-Nitrophenol 6.4 to 8.8 8.3 . . ., 570 C-YCresol red o-Cresolsulfonephthalein 7.2 to 8.8 8.2 434, 572 Y-R m-Cresolpurple m-Cresolsulfonephthalein 7.5 to 9.2 8.32 . . ., 580 Y-P Thymolblue Thymolesulfonephthalein 8.0 tO 9.6 8.9 430, 596 Y-B PhenolphthaleinPhenolphthalein 8.0 to 10.0 9.4 . . ., 553 C-R . α-Naphtholbenzeinα-Naphtholbenzein 9.0 to 11.0 Y-B Thymolphthalein Thymolphthalein 9.4 to10.6 10.0 . . ., 598 C-B Altzarin Yellow R 5-(p-Nitrophenylazo)- 10.0 to12.0 11.16 Y-V salicylic acid. Na salt Tropeolin 0 p-Sulfobenzeneazo-11.0 to 13.0 Y-O Br resorcinol Nitramine 2,4,6-Trinitrophenyl- 10.8 to13.0 C-O Br methylnitroamine

[0013] These compounds change color depending on the form they take (forexample, yellow when acidic and blue when basic). A pH paper is a filterpaper totally impregnated with one or more of these indicator compounds,generally an organic compound, that is a weak acid with a certain pKa(pKa is defined as the negative log of the dissociation equilibriumconstant). The pKa value determines the range of the indicator.

[0014] Specifically for our invention, we currently contemplate use of apH paper manufactured by Micro Essential Laboratory, Brooklyn, N.Y. witha pH range of 1-6. This pH paper is impregnated with meta-cresol purple(trade name) also known as meta-cresolsulfonephthalein (chemical name).The structure of this chemical is given below:

[0015] This indicator, meta-cresol purple, is red in acidic form andyellow in the basic form.

[0016] Our invention does not measure pH because the systems and thelike with which the acid test kit is intended to be used do not containan aqueous solution. We utilize pH paper because of the surprisingdiscovery that it has an indicator which will react with the inorganicacid vapor present in the refrigeration system. Furthermore, filterpaper impregnated with indicator solution is a commercially availableproduct, namely pH paper, thus lowering the cost even more.

[0017] Thus, the present invention takes advantage of the low cost andready availability of pH paper. If the indicator is in an acidicenvironment, the indicator will react with the acid and produce a redcolor. If the acid concentration is not enough to turn the indicatorcompletely red, however, an intermediate color, between red and yellow(that is some shade of orange) will be observed. Therefore, theintensity of the color is concentration dependent. On the pH paper, acertain amount of the indicator is impregnated, and as the acid reactswith the indicator, the indicator's color changes. When most of theindicator has reacted, a red color will be observed. Therefore, theintensity of the color change depends on what percentage of theindicator has been transformed (reacted) to the acidic form.

[0018] We have also found that in a refrigeration system the refrigerantvapor acid test should be performed from the suction (vapor) serviceport. If both a compressor suction-side and compressor discharge-sidevapor connection is available, we have further recognized that thelower-pressure suction side should be used and the system should beoperating in order to minimize the amount of oil discharged with therefrigerant vapor and will also serve to provide a more acidic sample.When the vapor-compression system is operating, the liquid refrigerantwith some dissolved oil is vaporized in the evaporator, resulting in anacid vapor refrigerant flow with entrained liquid oil droplets.

[0019] The acid level of the vapor stream during operation is not atequilibrium but instead is essentially the same as the acid level of theliquid that the refrigerant was flashed or evaporated from. Because thevapor is safer and much easier to sample, the sampling of the vaporphase during system operation is a much easier, safer, faster and betterapproach, as long as the system is operating, and will provideessentially the same accuracy as sampling of the liquid. In other words,although the equilibrium concentration of the acid in the vapor is lowerthan the acid concentration in the liquid refrigerant when the system isoff (and would, therefore, provide lower and inaccurate pH readings),when the system is running (i.e., compressor operating, refrigerantflowing), the liquid refrigerant with acid and dissolved oil is flashed(evaporated) into superheated refrigerant vapor and entrained oil, andthe acid is carried along with this vapor so that the acid level of thisvapor is essentially the same as the acid level in the liquidrefrigerant. Nevertheless, the acid test kit can be used in a systemwhich has been shut off or in relation to a tank of recoveredrefrigerant. For those non-operational systems which need to berepaired, the oil can be tested directly (or simply changed) while thesystem is being repaired and thus does require an acid indicator whichis safe and easy to use.

[0020] It is, therefore, an object of the present invention to providean accurate, yet simple and inexpensive, acid test device which cansample the refrigerant's acid level, by sampling the refrigerant vapor,from existing system service valves, or from a refrigerant recoverytank, to provide an indication of the condition of the refrigerant andtherefore the condition of the system.

[0021] In order to determine the pH of the vapor sample, it is necessaryfor a known amount of refrigerant be used in the test. We have furtherdeveloped a simple method of determining this known amount ofrefrigerant. All systems typically have service valves with valve coredepressors (often referred to as Schrader-valves). These valves, likeautomobile tire-valves, are opened when a valve core is depressed,usually by the device being attached to the valve. For refrigerationsystems, these types of service valves with valve core depressors areused in several standard sizes, with ¼″ being the most common and ⅜″,½″, and ⅝″ also used. For a given valve size, these service valves havea known flow cross-section. In order to determine the pH of the vaporsample, it is necessary to use a known amount of refrigerant. Thepresent invention also uses these service valves as the flow meteringdevice. In addition, for a given refrigerant, the system pressures areknown, from the saturation pressure temperature correlation for therefrigerant. Therefore the combination of the known cross-sectionorifice area (service valve cross-sectional flow area) and knownpressure can be used to calibrate refrigerant flow and therefore tocalibrate acid level with the time necessary to react the indicator,that is to obtain a specific color change on the indicator.

[0022] The present invention advantageously uses a readily available,inexpensive indicator paper held in a transparent tube-like fixture tomonitor the acid level. Indicator chemistry reaction is essentially afunction of acid level and exposure time in an essentially linearfashion. That is, half the acid level exposed for twice the time willresult in the same indicator reaction. Therefore, as discussed above,the effect of refrigerant flow must be considered in determining acidlevel. The present invention uses a standard refrigeration service valvewith valve-core depressor (Schrader-valve), an industry-standard servicevalve, which is already present in essentially all refrigerationsystems, as the natural throttling or metering device on the system. Thesystem pressure depends only on the system refrigerant, thusadvantageously allowing performance tables to be developed for eachrefrigerant.

BRIEF DESCRIPTION OF THE DRAWINGS

[0023] These and other objects, features and advantages of the presentinvention will become more readily apparent from the following detaileddescription thereof when taken in conjunction with the accompanyingdrawings wherein:

[0024]FIG. 1 is a side view of a slightly tapered indicator paper holderof the present invention in an unfolded position;

[0025]FIG. 2 is a plan view of the holder of FIG. 1 but in a partiallyfolded condition with a piece of indicator paper in between legs of theholder;

[0026]FIG. 3 shows a side view of the holder of FIGS. 1 and 2 and a topview thereof in the fully folded position;

[0027]FIG. 4 is a perspective view showing insertion of the fully foldedholder of FIG. 3 in an external tube;

[0028]FIG. 5 is a perspective view of the assembled holder and externaltransparent tube constituting a test kit with indicator paper showingattachment of a service valve;

[0029]FIG. 6 is a perspective view of the assembled external tube andservice valve of FIG. 5;

[0030]FIG. 7 is a side view similar to FIG. 5 but showing a secondembodiment of indicator holder;

[0031]FIG. 8 is a view similar to FIG. 5 but showing a third embodimentof indicator holder;

[0032]FIG. 9 is a view similar to FIG. 5 but showing a fourth embodimentof indicator holder;

[0033]FIG. 10 is a view similar to FIG. 5 but showing a fifth embodimentof indicator holder;

[0034]FIG. 11 consists of exploded views (a)-(e) showing another testkit embodiment in accordance with the present invention; and

[0035]FIG. 12 consists of exploded views (a)-(e) showing yet anothertest kit embodiment in accordance with the present invention.

DETAILED DESCRIPTION OF THE DRAWINGS

[0036] Referring now to FIG. 1, the acid indicator for a test kit isindicated generally by reference numeral 10 and consists of a holderhaving two slightly tapering panel portions 11, 12 joined by aconnecting strip 13 whose additional function is described below. Eachof the panel portions 11, 12 has an elongated aperture 14, 15,respectively, to expose a test paper to refrigerant vapor. A standardpH-type acid test paper 16 is pinched or sandwiched between the panelportions 11, 12 which are folded together as seen in FIG. 2 into thefinal folded position of FIG. 3 with the connecting stop 13 forming aprojecting nose or dimple.

[0037] The acid indicator insert 10 fitted with the pH test paper 16 isthen inserted into a clear tube 17 as seen in FIG. 4. The small raiseddimple or nose formed by the folded connecting strip 13 is arranged atthe tube inlet 18 as seen in FIG. 5 and is advantageously used todepress a valve core of the system's vapor-service-valve 19 which allowsrefrigerant vapor to flow through the test kit 10 in the manner shown bythe arrows A in FIG. 6 to contact the paper 16 exposed through theapertures 14, 15. The external clear tube 17 directs the refrigerantvapor past the indicator paper 16, and the refrigerant is then exhaustedinto ambient air. The total time for the test is less than 15 seconds.Refrigerant vapor, not liquid, is tested by holding the test kit 10against the system's vapor service valve 19, typically the valve oncompressor suction-side and only when the compressor (not shown) isoperating.

[0038] In one embodiment of the present invention, the folded insert 10is fabricated from a plastic material colored to the same color as theun-reacted indicator paper 16 held therewithin. Using theabove-mentioned pH paper having a range of pH of 1.2 to 2.8, forexample, the unreacted paper is yellow and after reaction the papercolor is orange or red. The test kit operator holds the test kit againstthe refrigeration system's vapor service Schrader-valve for a fivesecond count. If the indicator paper remains yellow by comparing it withthe surrounding yellow plastic panel portions 11, 12, then the acidlevel is deemed to be below 1-2 ppm, and the refrigerant and oil in thesystem are considered acceptably uncontaminated.

[0039] If the indicator paper turns orange within the five second count,however, acid is deemed present in the refrigerant vapor, and thereforealso in the oil, at an unacceptable level above safe operatingconditions. The refrigerant should then be cleaned or replaced. Ifrecovered refrigerant is being tested, the refrigerant should berecycled to an acceptable acid level before using in a system. If theindicator paper 16 turns red, there is a very high acid level in therefrigerant vapor and the oil. Both the oil and refrigerant should bechanged immediately, otherwise system failure is imminent, and thisrefrigerant should not be recycled. Finally, if the indicator paper 16remains yellow, the acid test kit can be exposed to refrigerant foranother five seconds while the system is running. If the indicator paper16 still remains yellow, the acid content is very low, below 0.5-1.0PPM. If, however, the indicator turns orange or red, clean up proceduresshould still be instituted.

[0040] A more accurate, but also somewhat more expensive, alternativeapproach is to color the plastic indicator holder 10, for example,orange for the type of pH paper used in this embodiment. The test kituser then holds the indicator 10 in the clear tube 17 on the servicevalve 19 and counts the number of seconds it takes for the paperindicator to turn the orange color of the surrounding plastic panelportions 11, 12. The time it takes to turn the indicator 10 to thespecified color (that is the color of the plastic holder), is comparedto a table for the particular refrigerant being tested to determine theacid content of the refrigerant. The test kit is configured so that ifno color change occurs after fifteen seconds the test is stopped becauseessentially no acid is present.

[0041] Several other configurations of indicators can be used as shownin FIGS. 7 through 10, where parts similar in function to the parts inFIGS. 1-6 are designated by the same numerals but primed. There are alsoseveral other standard indicator solutions, such as bromophenol blue andmeta-cresol purple, which can be used for acid testing. Ordinary pHpaper, which is typically used only for acid tests in aqueous solutions,has been found to work very well in the present invention because theresults are repeatable, accurate, and fast. Alternatively, any standardindicator solution can also be used directly on the test kit's insert 10by configuring the panel portions 11, 12 of paper which is directlytreated with indicator chemistry. A currently contemplated embodiment isthat shown in FIGS. 1-6 and contemplates using commercially available pHpaper sandwiched into the color-coded bracket 10 which is slipped intothe clear, slightly elastic tube 17 which is sized to be deformed intoan oval cross-section upon insertion of the slightly tapered paperholder 10 into the tube 17 to insure a tight friction fit.

[0042] In the embodiment of FIG. 7, the holder 10′ is a solid piece overwhich a piece of indicator paper 16′ is laid before insertion into thetube 17′. In the embodiment of FIG. 8, the holder 10″ is in the form ofa cylindrical member installed in the clear tube 17″ such that a pieceof indicator paper 16″ can be wrapped over the holder 10″. Theembodiment of FIG. 9 is similar to the embodiment of FIG. 7, except thatthe holder 10″′ has a projecting nose 13″′ similar in function to thenose or dimple used in the embodiment in FIGS. 1-6. The indicator paper16″′ has an opening through which the nose 13″′ extends. The embodimentof FIG. 10 is similar to the embodiment of FIG. 8 except that theindicator paper 16″′ has an aperture through which the cylindricalmember 16″′ is inserted before insertion into the clear tube 17″.

[0043] The indicator paper holder 10 can, for example, be fabricatedfrom flat colored plastic or metal which is folded into the frameholding the indicator paper as shown in FIGS. 1-6. This embodiment,which forms a rounded nose 13 has a wider surface for depressing theSchrader valve and allows use of a thinner material, such as 0.020″.Because of the rounded nose 13, however, the frontal area whichdepresses the Schrader-valve is much thicker, e.g. approximately 0.090″depending upon the material used and its ductility. This insert can alsobe slightly tapered along its long sides, as seen in FIG. 1, to alloweasier insertion into the clear somewhat elastic tube 17, the width ofthe insert 10 being, for example, about 0.050″ wider that the diameterof the tubing 17 to insure a tight friction fit.

[0044] A currently preferred embodiment of the present invention asshown in FIG. 11, the test kit 20 is fabricated from two matinginjection-molded and symmetrical parts 21, 22 molded from clear plasticmaterial. Each half 21, 22 of the injected molded holder 20 has a raiseddimple 23, 24 at the tube inlet which is used to depress the system'svapor-service-valve valve-core and allows refrigerant vapor to flow. Onone side of both halves 21, 22 of the molded holder 20 are crush pins 25which deform into mating holes 26 on the other half to lock the halvestogether as best seen in the views (d) and (e) in FIG. 11. No glue oradhesive is used to avoid adversely affecting the pH paper 27. A shelfor frame 28 is also molded into both halves 21, 22 to pinch and hold theindicator paper 27 in place.

[0045] To further simply the fabrication of the molded holder, a thirdembodiment of the present invention as seen in FIG. 12 is provided. Tosimplify fabrication, the raised dimple sections 23, 24 of FIG. 11 hasbeen replaced by a complete center shelf 29 which also serves as anadditional pinch point for the indicator paper. All other features ofthis embodiment remain the same as in FIG. 11 and therefore aredesignated by the same numerals but primed.

[0046] After fabrication, the acid test kit in each of theabove-described embodiments is packaged in an airtight plastic bag toavoid contamination prior to use.

[0047] Although the invention has been described and illustrated indetail, it is to be clearly understood that the same is by way ofillustration and example, and is not to be taken by way of limitation.The spirit and scope of the present invention are to be limited only bythe terms of the appended claims.

We claim:
 1. A test kit, comprising a hollow transparent member open at upstream and downstream ends thereof, and an acid indicator assembly removably and securely held within the member, wherein the upstream end of the member is configured to be held temporarily against a service valve at one of a compressor suction side inlet of a refrigeration system and a recovered refrigerant vessel for permitting a flow of gaseous refrigerant through the member into the atmosphere.
 2. The test kit according to claim 1, wherein the acid indicator assembly comprises a tapered holder fixture having two panels arranged to be folded together with a pH-type acid indicator paper therebetween, said fixture being sized to provide a tight friction fit with the transparent member.
 3. The test kit according to claim 2, wherein the fixture defines a dimple between the panels at the upstream side of the member, the dimple being configured to open the service valve constituted by a Schrader-valve.
 4. The test kit according to claim 2, wherein each of the panels has an aperture to expose the indicator paper held therebetween to the gaseous refrigerant flow from the service valve.
 5. The test kit according to claim 4, wherein the dimple constitutes a bridging portion joining the panels.
 6. The test kit according to claim 3, wherein the transparent member is a cylindrically-shaped tube.
 7. The test kit according to claim 2, wherein the panels have a color matching a color of the paper in an unreacted state.
 8. The test kit according to claim 2, wherein the panels have a color matching a color of the paper in an reacted state.
 9. The test kit according to claim 1, wherein the acid indicator assembly includes a flat rigid holder and pH-type acid paper extending along one side of the holder over an upstream face of the holder and along another side of the holder.
 10. The test kit according to claim 9, wherein the holder has a dimple at the upstream face, and the paper has an aperture through which the dimple extends to open the service valve constituted by a Schrader-valve.
 11. The test kit according to claim 1, wherein the acid indicator assembly is a cylindrical piece extending transversely of the transparent member, and pH-type acid paper is arranged to extend around the piece in a downstream direction of the transparent member.
 12. The test kit according to claim 1, wherein the acid indicator assembly is a cylindrical piece extending transversely of the transparent member, and a pH-type acid paper with an aperture through which the piece is arranged to extend a downstream direction of the transparent member.
 13. A test kit, comprising a transparent member consisting of two portions arranged to be joined together and open at upstream and downstream ends thereof, each of the portions having a raised dimple segment at the upstream end and a shelf at each joint face for holding a pH-type acid paper securely therebetween, wherein the raised dimple segments, in an assembled state, constitute a dimple configured to open a Schrader-valve when the kit is temporarily held against the valve for permitting a flow of gaseous refrigerant therethrough to the atmosphere.
 14. A test kit, comprising a transparent member consisting of two portions arranged to be joined together and open at upstream and downstream ends thereof, each of the portions having a raised dimple segment extending from the upstream end to the downstream end to define a shelf and a shelf at each joint face for holding, together with the raised dimple segments, a pH-type acid paper securely therebetween, wherein the raised dimple segments, in an assembled state, constitute a dimple configured to open a Schrader-valve when the kit is temporarily held against the valve for permitting a flow of gaseous refrigerant therethrough to the atmosphere.
 15. A method for testing for presence of acid in refrigerant of a refrigeration system or a recovered refrigerant vessel, comprising the steps of removably inserting pH-type acid paper in a transparent member open at both ends; placing the transparent member against a service valve at one of the refrigeration system and the recovered refrigerant vessel to open the service valve for permitting gaseous refrigerant to flow therethrough; and holding the transparent member against the service valve for a predetermined period as vapor refrigerant flows therethrough to the atmosphere and observing a color change in the paper.
 16. A hollow transparent tube open at upstream and downstream ends thereof and internally configured to removably and securely hold therein acid indicator assembly for a refrigerant vapor test kit, wherein the upstream end of the tube is configured to be held temporarily against a service valve at one of a compressor suction side inlet of a refrigeration system and a recovered refrigerant vessel for permitting a flow of gaseous refrigerant through the member into the atmosphere.
 17. An acid indicator assembly for a test kit, comprising a tapered holder fixture having two panels arranged to be folded together, and a pH-type acid indicator paper held between the panels, said fixture being sized to provide a tight friction fit with a viewing member open at both ends and configured to be held temporarily against a service valve at one of a refrigeration system and a recovered refrigerant vessel for permitting a flow of gaseous refrigerant through the member into the atmosphere.
 18. The assembly according to claim 17, wherein the fixture defines a dimple between the panels at one side of the member, the dimple being configured to open the service valve constituted by a Schrader-valve.
 19. The assembly according to claim 17, wherein each of the panels has an aperture to expose the indicator paper held therebetween to the gaseous refrigerant flow from the service valve.
 20. The assembly according to claim 19, wherein the dimple constitutes a bridging portion joining the panels.
 21. The assembly according to claim 17, wherein the panels have a color matching a color of the indicator paper in an unreacted state.
 22. The assembly according to claim 17, wherein the panels have a color matching a color of the indicator paper in an reacted state.
 23. An acid indicator assembly for a test kit, comprising a flat rigid holder, and pH-type indicator paper extending along one side of the holder over an upstream face of the holder and along another side of the holder, said rigid holder being sized to provide a tight friction fit in a viewing member open at both ends and configured to be held temporarily against a service valve at one of a refrigeration system and a recovered refrigerant vessel for permitting a flow of gaseous refrigerant through the member into the atmosphere.
 24. The assembly according to claim 23, wherein the holder has a dimple at one face, and the paper has an aperture through which the dimple extends to open the service valve constituted by a Schrader-valve.
 25. An acid indicator assembly comprising a cylindrical piece sized and configured to extend transversely of a viewing member open at both ends, and pH-type acid paper arranged to extend around the piece in a downstream direction of the viewing member which is configured to be held temporarily against a service valve at one of a refrigeration system and a recovered refrigerant vessel for permitting a flow of gaseous refrigerant through the member into the atmosphere.
 26. An acid indicator assembly, comprising a cylindrical piece sized and configured to extend transversely of a viewing member open at both ends, and a pH-type acid paper with an aperture through which the piece is arranged to extend a downstream direction of the viewing member which is configured to be held temporarily against a service valve at one of a refrigeration system and a recovered refrigerant vessel for permitting a flow of gaseous refrigerant through the member into the atmosphere.
 27. Method of using pH-type indicator paper in a test kit for reacting with inorganic acids in refrigerant vapor.
 28. Method of using, for impregnating a paper for a test kit to react with inorganic acids in refrigerant vapor, a pH indicator selected from the group consisting of o-Cresolsulfonephthalein m-Cresolsulfonephthalein Thymolsulfonephthalein Diphenylamino-p-benzene sodium sulfonate 2,6-Dinitrophenol 2,4-Dinitrophenol Dimethylaminoazobenzene Dimethylaminoazobenzene sodium sulfonate Tetrabromophenolsulfonephthalein Tetrabromo-m-cresolsulfonephthalein o-Carboxybenzenazodimethylaniline Dichlorophenolsulfonephthalein Dibromo-o-cresolsulfonephthalein Dibromophenolsulfonephthalein p-Nitrophenol Dibromothymolsulfonephthalein Aminodimethylaminotoluphenazonium chloride Phenolsulfonephthalein m-Nitrophenol o-Cresolsulfonaphthalein m-Cresolsulfonephthalein Thymolsulfonephthalein Phenolphthalein a-Naphtholbenzein Thymolphthalein 5-(p-Nitrophenylazo)salicylic acid, Na salt p-Sulfobenzeneazoresorcinol 2,4,6-Trinitrophenylmethylnitroamine 